Since the average pupil distance of one's left and right eye is about 6.0 cm-7.0 cm, resulting in two images received by the retinas are slightly different because of the difference in viewing angles. The fusion of two perspective images to produce depth perception is one of the essential functions of human brain. The stereoscopic effect is formed when one watches an object.
In the field of autostereoscopic display technology, the existing 3D display technologies are divided into two categories; glasses type and autostereoscopic type. For autostereoscopic display technology, the lenticular lens and the parallax barrier are adopted by most of the display products.
In general, the grating lens is needed to present stereoscopic images by matching with the LCD panel. The manufacturing and assembly processes of the LCD panel and grating lens are sophisticated and costly. The quality of the 3D effect perceived by observers is determined by the accuracy of pixels alignment with the lens. This results in, especially for large-sized display panels, the high rejection rate due to misalignment during the assembly process. In addition, the size of the panel and precision of the grating lens are restricted by the manufacturing facilities. Therefore, the grating lens technology is unsuitable for the large-sized display products.
Although, the medium-sized LCD panel with grating lens in front is an effective measure for the realization of glasses free 3D. But, in the meantime, the 2D images or texts will be deteriorated by the grating lens. On the other hand, the existing techniques for switching 2D/3D display modes are mostly implemented by using optoelectronic components or moving optics. But it is still not widely implemented in today's products. All the similar disadvantages will be occurred when the large-sized LED display adopt the grating lens in front of the screen to achieve glasses free 3D and 2D/3D auto-conversion.
In Chinese Patent No. CN103995361 B, an autostereoscopic pixel unit is invented and assembled to from a glasses free 3D display device. Each optical guiding area converge the light from light mixing area and deflects into directions toward the each eye of the viewers. The binocular parallax image is then formed by the left and right eyes of the viewers, therefore a stereoscopic image is then perceived by one's brain. Since an autostereoscopic pixel units is minimized to a component level, through assembling a specific number of pixel units into display module, and several display modules can be spliced to vast display area to present 3D images without installing grating lens in front of the screen. In addition, the full color LEDs and autostereoscopic pixel emitting units are arranged alternately by row and column on the circuit board to form a display module, and assembled into a large-sized screen. The system switch the 2D and 3D image modes by alternatively lighting up or off via the full color LEDs and autostereoscopic pixel emitting units. When the full color LEDs is on, the autostereoscopic pixel emitting unit will be off. At that moment, the screen presents 2D images. Conversely, when autostereoscopic pixel emitting unit is on, the screen presents 3D images. But, it is difficult to control and balance the difference in brightness, contrast and color of the adjacent full color LEDs and autostereoscopic pixel emitting units. On the other hand, the pitch of autostereoscopic pixel emitting unit for presenting 3D images and the pitch of the full color LEDs to present 2D images are increased correspondingly, this result in reducing the resolution of the whole display.
These shortcomings mentioned above are still the technical barriers of glasses free 3D large-sized screen which needs to be overcome. In this regard, the autostereoscopic pixel emitting unit which is able to transmit the 2D images and the 3D parallax images simultaneously, and the 2D/3D auto-conversion may be realized for the whole screen or for several portions of the display area, is a novel solution desired. These functions are essentially important when mixing various 2D or 3D contents in series for showing on a large screen without optical solution arranged in front.